1. Field of the Disclosure
The disclosure relates to measuring changes in lung volume and, more particularly, to techniques for measuring changes in lung volume using ultrasound transducers.
2. Brief Description of Related Technology
Respiratory failure is common with premature births and is a leading cause for the prevalence of ventilatory assistance among infants. For example, approximately 25% of premature neonates require mechanical ventilation due to respiratory failure. Healthcare professionals must take particular care in treating the premature neonates, because of this prevalence of the lung immaturity and the resulting harmful effects. This includes monitoring lung volume changes in neonates receiving mechanical ventilation to assess the effectiveness and safety of therapeutic treatments.
Yet, despite the respiratory problems in premature infants and neonates, presently there are no benign, reliable ways to monitor local ventilation in this population. For decades, researchers have suggested techniques for monitoring lung performance in infants, but there have been no significant breakthroughs, certainly not in terms of producing cost effective, reliable solutions. Part of the problem is the physiology involved, especially for infants. Neonates experience poor gas exchange because of atelectasis and obstructive airway disease, caused by a lack of pulmonary surfactant and immature airways. Advancements in treatment of these conditions have occurred, especially with the advent of antenatal steroid therapy and exogenous surfactant administration. But despite these treatments, large percentages of neonates still require high-frequency ventilation (HFV).
One of the problems with neonate treatment, and one of the reasons why lung volume measurement techniques are sought after is the occurrence of lung injury produced by mechanical ventilation. A condition called bronchopulmonary dysplasia (BPD) results from the effects of positive pressure ventilation and other factors required for the treatment of respiratory distress syndrome (RDS). This is not uncommon with fragile patient populations of others on ventilators, that an effective treatment option can cause other secondary conditions. In this example, the principal causes of the secondary condition (BPB) relate directly to uncertainties involved in optimizing lung volume. The issues are compounded further, however, by the myriad of different ventilators and ventilatory modes employed to ventilate infants.
As to HFV in particular, this is a type of ventilation technique that uses small tidal volumes delivered at extremely rapid rates, typically 10-20 Hz. HFV techniques have been compared and contrasted with conventional mechanical ventilation (CMV). Animal studies have suggested that HFV has fewer complications than CMV, by reducing ventilator-induced lung injury. HFV, also, has better gas exchange in the presence of air leaks; and HFV decreases oxygen requirements. However, developing a proper strategy for HFV treatment remains elusive. The technique is still highly controversial. There is no standardize criteria for optimal use of HFV; and this problem is exacerbated by the lack of accurate clinical measurements of lung volume.